Hydrophilic additives

ABSTRACT

The invention relates to hydrophilic additives for synthetic fibres containing polyolefin; said additives are represented by general formula (I): A-B-C-B-A wherein A is a radical R—COO, wherein R represents a saturated, cross-linked or non-cross-linked alkyl radical having 7-21 C atoms, B represents a group (C n H 2n O) k , wherein n is a whole number from 2-4 and k can have a value of 1-15, C represents a linear or cross-linked alkylene radical having at least 2 and at the most 6 C atoms and the radical C can be, optionally, interrupted by oxygen atoms.

[0001] This invention relates to additives for the permanent internalhydrophilicization of polyolefin-containing materials, preferablypolypropylene fibers.

[0002] In many cases, the surface of plastic products has to be providedwith special effects which either can only be produced incompletely, ifat all, during molding for technical reasons or can only be producedunfavorably for economic reasons. One such effect, for example, is theimprovement of wettability with polar liquids, such as water. Technicalapplications in this respect include, for example, the production ofhygiene articles.

[0003] In the production of hygiene articles, such as diapers orsanitary napkins, and also wiping cloths or “geofleeces”, absorbentmaterials are used to take up aqueous liquids. In order to preventdirect contact with the absorbent material during wear and to increasewearing comfort, this material is enveloped in a thin water-permeablenonwoven. Such nonwovens are normally made from synthetic fibers, suchas polyolefin or polyester fibers, because these fibers can beinexpensively produced, show good mechanical properties and areheat-resistant. However, untreated polyolefin or polyester fibers arenot suitable for this application because they are not sufficientlypermeable to water-containing fluids on account of their hydrophobicsurface.

[0004] In principle, the fibers can be given the necessary hydrophilicproperties by subsequent coating with corresponding finishes (externaladditives) or can be made sufficiently hydrophilic by the incorporationof suitable additives (internal additives) during their production. Thesecond of these two options is described in WO 95/10648 which disclosesdiesters of polyethylene glycol with fatty acids or derivatives thereofas suitable permanent additives. In the Examples, reaction products ofoleic acid with polyethylene glycol having a molecular weight of 400 aredescribed as particularly advantageous. Applicants' hitherto unpublishedDE 100 155 54 describes reaction products of two parts lauric acid withpolyethylene glycols which are suitable as internal additives forhydrophilicizing polyolefin fibers.

[0005] Additives such as these are generally processed with polyolefingranules to form a masterbatch which is then added as such to thepolymer granules before processing to the fibers or other end products,followed by extrusion. However, it is desirable for reasons of cost tobe able to incorporate such additives during the actual extrusionprocess in the extruder. Unfortunately, attempts to incorporate knownadditives by direct addition have been frustrated by problemsattributable to the low-temperature stability of the additives. Thecompounds have cold cloud points above 20° C. Accordingly, when they areincorporated by direct addition, the compounds crystallize out and blockthe dies.

[0006] Accordingly, the problem addressed by the present invention wasto provide additives for the permanent hydrophilicization of polyolefinfibers which would not have any of the disadvantages mentioned above.These additives would be capable of providing the fibers or productswith sufficient hydrophilia which they would retain even under stress,for example after the repeated wetting with water which they undergo inwashing processes.

[0007] It has been found that certain oligomeric esters exhibit therequired properties.

[0008] In a first embodiment, the present invention relates to internalhydrophilicizing additives for synthetic polyolefin-containing fiberswhich correspond to general formula (I):

A-B-C-B-A  (I)

[0009] where A represents a group R—COO in which R is a saturated,branched or unbranched C₇₋₂₁ alkyl group, B represents a group(C_(n)H_(2n)O)_(k) in which n is an integer of 2 to 4 and k has a valueof 1 to 15, and C is a linear or branched alkylene group containing atleast 2 and at most 6 carbon atoms which may also be interrupted byoxygen atoms. The index k relates to the individual group B and does notindicate the total number of groups B in the molecule. The index kvaries on account of the varying, technically related degrees ofalkoxylation of the individual molecules and, accordingly, may also bean odd number.

[0010] The compounds corresponding to general formula (I) are obtained,for example, by reaction of diols, for example polyalkylene glycols,with alkoxides and with saturated fatty acids. On the one hand, diolscontaining 2 to 6 carbon atoms, which form structural unit C of theadditives according to the invention, and ethylene, propylene and/orbutylene oxide which form the groups B in the compounds according to theinvention must be present. The free hydroxyl groups of the alkoxides areterminated by saturated C₈₋₂₂ fatty acids.

[0011] The diols are preferably selected from the group consisting ofethane-1,2-diol, propane-1,2-diol, propane-1,3-diol and butane-1,4-diol.In principle, mixtures of the diols may also be used although it hasproved to be of advantage to use only one diol for the reaction.Depending on the diol with which the synthesis process was started, thecompounds (I) obtained contain different groups C. This difunctionalgroup is preferably a CH₂—CH₂, CH₂—CH(CH₃), CH₂—CH₂—CH₂ or (CH₂)₄ group.

[0012] However, it can also be of advantage for the group C to containone or more oxygen atoms. This preferably applies to an additive startedon the basis of diethylene glycol, dipropylene glycol or similar ethercompounds. In this case, C in formula (I) is a difunctional groupCH₂—CH₂—O—CH₂—CH₂—O or (CH₂)₃—O—(CH₂)₃—O.

[0013] The alkoxides are selected from the group consisting of ethyleneoxide, propylene oxide and butylene oxide and mixtures thereof. Ifalkoxides of different types are reacted, the alkoxylation reaction maybe carried out both blockwise and at random. The number of alkoxideunits in the compounds of formula (I) varies from 2 to 30 so that k mayassume a value of 1 to 15. Preferred compounds of formula (I) are thosein which k has a value of 2 to 15, preferably 4 to 10 and moreparticularly 10 or 5. Other preferred compounds of formula (I) alsocontain ethylene oxide units as the group B, preferably only ethyleneoxide units. However, compounds containing only propylene oxide groupsmay also be used. In addition, mixed alkoxylates, preferably ethyleneoxide and propylene oxide groups, are preferred. In these cases, thenumber of ethylene oxide groups should at least be equal to the numberof propylene oxide groups (PO) and an excess of ethylene oxide groups(EO) should preferably be present. EO PO ratios of 5:1 to 2:1 arepreferred.

[0014] Suitable saturated fatty acids which can form group A of thecompounds according to the invention are preferably selected from thegroup consisting of octanoic acid, nonanoic acid, decanoic acid,undecanoic acid, dodecanoic aid, tridecanoic acid, tetradecanoic acid,pentadecanoic acid, hexadecanoic acid, heptadecanoic acid andoctadecanoic acid; nonadecanoic acid, eicosanoic acid and heneicosanoicacid; and docosanoic acid. Compounds corresponding to formula (I), inwhich R is a saturated C₉₋₁₃ or C₉₋₁₁ alkyl group, are preferred.Compounds corresponding to formula (I) based on decanoic acid (C₁₀) andundecanoic acid (C₁₁) are most particularly preferred.

[0015] Unsaturated acids may also be used although compounds of formula(I) of which the substituents have unsaturated functionalities do showinadequate oxidation stability.

[0016] In order to overcome the problems mentioned above, the compoundscorresponding to formula (I) should preferably have a cold cloud pointbelow 20° C. In the context of the present invention, the cold cloudpoint is determined as follows to DIN EN 23015: a test tube containing alow-temperature thermometer and the product to be tested is placed in acooling solution (ethylene glycol/water ca. 1:1, ca−20° C. from arefrigerator) and cooled until distinctly visible clouding occurs. Thetemperature at which the product is completely clear again is thendetermined by stirring with the thermometer at room temperature (21°C.).

[0017] Preferred compounds of formula (I) have a cold cloud point below12° C., preferably below 10° C. and more particularly below 6° C. It isof particular advantage to use compounds of formula (I) which have acold cloud point below 5° C. and more particularly below 3° C.

[0018] Preferred compounds of formula (I) suitable as additives inaccordance with the invention are those in which R is a linear alkylgroup containing 9 carbon atoms, k has a value of 5, n has a value of 2and C is a group CH₂—CH(CH₃) or in which R is a linear alkyl groupcontaining 11 carbon atoms, k has a value of 5, n has a value of 2 and Cis a group CH₂—CH₂(CH₃). Other preferred hydrophilicizing additives arecompounds (I) in which A is a group R—COO, where R is a saturated,branched or unbranched C₇₋₂₁ alkyl group, B is a group C₃H₆ and C is agroup CH₂—CH₂—O—CH₂—CH₂—O. Another preferred additive of formula (I)contains a diethylene glycol residue as part C, 5 to 7 parts EO and 2 to4 parts PO as the groups B and a lauric acid residue as the substituentR.

[0019] The additives according to the invention may be used on their ownor in admixture with one another. In addition, other additives knownfrom the prior art for the extrusion or production of polymers may beadded.

[0020] According to the invention, the additives are used for permanenthydrophilicization in polyolefin-containing materials, preferablyfibers, sheet-form materials, such as nonwovens, films and foams.

[0021] The additives according to the invention are preferably used innonwovens and foams. As generally known among experts, foams areplastics which can be charged with additives by virtue of the cellspresent inside. Charging should be carried out simply by adding at leastone additive to the plastic foam according to the invention, whichrepresents a porous carrier material, and mixing it with the foam at atemperature below the melting point of the basic polymer used for theproduction of the plastic foam, but above the melting point of theadditive. The additive flows into the cells inside the plastic foam,i.e. the plastic foam by virtue of its special structure absorbs theliquid additives like a sponge.

[0022] Suitable polyolefin-containing materials are any known polymersand copolymers based on ethylene or propylene. Mixtures of purepolyolefins with copolymers are also suitable in principle. Thehydrophilicizing additives may also be used in mixtures of polyolefinswith other synthetic or natural polymers, for example cellulose or hemp,in order to provide the polyolefin fibers with permanently hydrophilicproperties.

[0023] Polymers particularly suitable for the purposes of the teachingaccording to the invention are listed below: poly(ethylenes), such asHDPE (high-density polyethylene), LDPE (low-density polyethylene), VLDPE(very-low-density polyethylene), LLDPE (linear low-densitypolyethylene), MDPE (medium-density polyethylene), UHMPE (ultra highmolecular polyethylene), VPE (crosslinked polyethylene), HPPE(high-pressure polyethylene); poly(propylenes), such as isotacticpolypropylene; syndiotactic polypropylene; Metallocen-catalyzedpolypropylene, high-impact polypropylene, random copolymers based onethylene and propylene, block copolymers based on ethylene andpropylene; EPM (poly[ethylene-co-propylene]); EPDM(poly[ethylene-co-propylene-co-unconjugated diene]).

[0024] Other suitable polymers are: poly(styrene); poly(methylstyrene);poly(oxymethylene); Metallocen-catalyzed α-olefin or cycloolefincopolymers, such as norbornene/ethylene copolymers; copolymerscontaining at least 60% ethylene and/or styrene and less than 40%monomers, such as vinyl acetate, acrylates, methacrylates, acrylic acid,acrylonitrile, vinyl chloride. Examples of such polymers are:poly(ethylene-co-ethyl acrylate), poly(ethylene-co-vinyl acetate),poly(ethylene-co-vinyl chloride), poly(styrene-co-acrylonitrile). Alsosuitable are graft copolymers and polymer blends, i.e. mixtures ofpolymers in which the above-mentioned polymers inter alia are present,for example polymer blends based on polyethylene and polypropylene.

[0025] Homopolymers and copolymers based on ethylene and propylene areparticularly preferred for the purposes of the present invention. In oneembodiment of the present invention, therefore, polyethylene on its ownis used as the polyolefin; in another embodiment, polypropylene on itsown is used as the polyolefin and, in a further embodiment,ethylene/propylene copolymers are used as the polyolefin.

[0026] In one particularly preferred embodiment of the invention, theadditives are used in polypropylene fibers. Such fibers preferably havea melt flow rate of greater than 10 to 1,500 dg/min. (as measured at230° C./2.16 kg load). Preferred fibers can have melt flow rates of, forexample, 150 to 1,200 or 20 to 25 or 400 to 1,000 dg/min.

[0027] In a second embodiment, the present invention relates to aprocess for the production of hydrophilicizing additives correspondingto formula (I) for synthetic polyolefin-containing fibers, characterizedin that a diol selected from the group consisting of ethane-1,2-diol,propane-1,2-diol, propane-1,3-diol and butane-1,4-diol or diethyleneglycol or dipropylene glycol is reacted with alkoxides selected from thegroup consisting of ethylene oxide, propylene oxide and/or butyleneoxide and the resulting reaction product is esterified with a saturated,linear or branched fatty acid containing 8 to 22 carbon atoms.Mixed-alkoxylated products preferably containing ethylene oxide andpropylene oxide groups are preferably used for the purposes of theteaching of the invention. Additives of formula (I), in which C is analkylene group interrupted by oxygen atoms and G is a C₃H₆ group, areparticularly preferred. In compounds such as these, C is preferably adiethylene glycol residue and A is a defined above.

[0028] The use of the compounds of formula (I) according to theinvention as internal additives in polyolefin-containing fibers leads toimproved hydrophilicization of the fibers, good water absorption beingobtained at the same time. Accordingly, fibers with additives thusinternally incorporated are suitable for a number of technicalapplications, more particularly in the field of hygiene nonwovens andwiping cloths.

[0029] The present invention also relates to a process for theproduction of articles completely or partly containing polyolefins,characterized in that compounds corresponding to formula (I) are addedto polymer granules completely or partly containing polyolefins inquantities of 0.1 to 5% by weight, based on the granules, followed byprocessing in known manner to fibers or films, preferably by extrusion.

[0030] It has proved to be of advantage to aftertreat the extrudedadditive-containing fibers or films with water. This aftertreatmentshould preferably be carried out directly and immediately after theextrusion step in order to achieve optimal hydrophilicization. Thetreatment with water is preferably carried out by contacting theextruded products with water at 80 to 90° C. This can be done byspraying, immersion or via kiss rollers. The products may also betreated with steam, preferably superheated steam. The treated productsare then dried.

[0031] The articles, preferably fibers or films or sheet-form materials,such as nonwovens, of these fibers contain the additives in quantitiesof preferably 0.1 to 5% by weight, more preferably 0.5 to 5% by weightand most preferably 1.0 to 2.5% by weight, based on the total weight ofthe articles.

[0032] The present invention also relates to the use of the compoundscorresponding to formula (I) as internal hydrophilicizing additives inpolyolefin-containing fibers or sheet-form materials, more particularlyin nonwovens. Although the compounds of formula (I) may also be used asexternal additives, i.e. for example as constituents of an externallyapplied finish, this is not the subject of the present application.

[0033] Nonwovens can be produced by any of the methods for producingnonwovens known in the prior art as described, for example, in Ullmann'sEncyclopedia of Industrial Chemistry, Vol. A 17, VCH Weinheim 1994,pages 572-581. Nonwovens produced by the dry-laid process or by thespunbond process or by the melt flow process are preferred. The dry-laidprocess starts out from staple fibers which are normally first separatedinto individual fibers by carding and are then laid together to form theunstabilized nonwoven using an aerodynamic or hydrodynamic process. Theunstabilized nonwoven is then heat-treated (“thermobonded”) to give thefinal nonwoven. To this end, the synthetic fibers are either heated tothe extent that their surface melts and the individual fibers are joinedtogether at their points of contact or the fibers are coated with anadditive which melts during the heat treatment and thus bonds theindividual fibers together. The individual bonds are fixed by cooling.Besides this process, any other processes used in the prior art forbonding nonwovens may of course also be used. By contrast, the spunbondprocess starts out from individual filaments formed by melt-spinningfrom extruded polymers which are forced under high pressure throughspinning jets. The filaments issuing from the spinning jets are bundled,stretched and laid to form a nonwoven which is normally stabilized bythermobonding.

EXAMPLES

[0034] Synthesis of the additives

[0035] General synthesis procedure for additives 1-4 according to theinvention: X mol fatty acid are reacted with y mol diol under nitrogenat 240° C. in the presence of 0.5% H₃PO₂ (50%). When water stopsdistilling over, the temperature is reduced to 100° C. and a vacuum (15mbar) is applied. When the acid value remains constant for an hour, thereaction may be terminated. To this end, the H₃PO₂ is neutralized with atwofold excess of anhydrous sodium carbonate at 80° C. (ca. 30 mins.).The salts are then filtered off with the assistance of a filter aid(Hyflo Celite).

[0036] Additive 1

[0037] 2.05 mol dodecanoic acid are reacted with 1.00 molpropane-1,2-diol ×10 EO for 9 h by the procedure described above. Acidvalue 1.7, OH value 7.9.

[0038] Additive 2

[0039] 2.05 mol dodecanoic acid are reacted with 1.00 molpropane-1,2-diol ×12 EO for 9 h by the procedure described above. Acidvalue 1.5, OH value 6.6.

[0040] Additive 3

[0041] 1.95 mol dodecanoic acid are reacted with 1.00 molpropane-1,3-diol ×10 EO for 8 h by the procedure described above. Acidvalue 1.5, OH value 11.4.

[0042] Additive 4

[0043] 2.00 mol dodecanoic acid are reacted with 1.00 molpropane-1,3-diol ×10 EO for 7 h by the procedure described above. Acidvalue 1.6, OH value 15.2.

[0044] Wetting test

[0045] The effectiveness of additives 1 to 4 according to the inventionin polypropylene granules was demonstrated by the wetting test describedbelow.

[0046] 1. 600 g of high molecular weight polypropylene granules(commercial product “Eltex PHY 671” of Solvay) are mixed with 9.0 g(=1.5% by weight) of the substance to be tested for hydrophilicfinishing. This mixture is introduced into an extruder (DSK 42/7twin-screw extruder of Brabender OHG, Duisburg) through a hopper. Aswell-known to the expert, an extruder is a machine for processingplastics which is suitable for continuously mixing and plasticizing bothpowder-form and granular thermoplastics. Beneath the feed hopper, thereis a contra-rotating twin screw longitudinally divided into threeheating zones in addition to a water-cooling system which is intended toprevent premature melting of the granules or powder. The temperature ofthe heating zones and the rotational speed of the twin screw can becontrolled through a data-processing Plast-Corder PL 2000 which isconnected to the extruder via a PC interface. Heating zones I, II andIII are each heated to a temperature of 200° C., the three heating zonesbeing air-cooled to keep the temperature constant. The mixture ofpolypropylene granules and test substance is automatically taken intothe extruder by the contra-rotating twin screw and transported along thescrew. The rotational speed is 25 r.p.m. to guarantee thoroughcompounding and homogenization. The resulting homogeneous mixturefinally enters a nozzle which represents a fourth heating zone. Thetemperature of the nozzle is adjusted to 200° C., i.e. the mixtureleaves the extruder at that temperature. The extrusion die is soselected that the mean diameter of the strand after leaving the die isof the order of 2-3 mm. The strand is granulated, i.e. chopped intosmall pieces between about 2 and 4 mm in length. The granules obtainedare cooled to 20° C. The granules are gravimetrically converted (i.e. bythe force of gravity) into fibers in a melt spinning machine at aprocessing temperature of 280° C. (i.e. both the melt star temperatureand the temperature of the spinning jet are adjusted to 280° C.). Thefibers obtained have a denier of about 10 to 30 dtex (1 dtex correspondsto 1 g of fibers per 10,000 m fiber length). 500 m of these fibers arethen wound into a roll with a diameter of 6.4 cm. The fiber wound intothe roll is removed from the roll and the circular figure removed isstabilized by knotting at its center to form a figure-of-eight; this isreferred to hereinafter as the “skein”.

[0047] 2. A 1 liter measuring cylinder (glass cylinder with an internaldiameter of 6.0 cm) is filled with distilled water at 20° C. to the 1000ml mark. The skein to be tested is then held in such a way that itslongitudinal axis coincides with the vertical of the measuring cylinder,i.e. the skein appears as a vertical “8”. A weight consisting of copperwire is then attached to the lowermost part of the “8”, the weight ofthe copper wire being 0.2064 g per gram of skein. The copper wire isattached in the form of coils to the skein, the coil diameter of thecopper wire being about 1 to 2 cm. The coils of copper wire are thenpressed together by gentle compression between the thumb and indexfinger. The skein with the copper weight is then held over the watersurface of the measuring cylinder in such a way that the lower part ofthe copper weight dips into the water and the lowermost part of theskein is about 2 mm above the water surface. The skein is then releasedand the time in seconds it takes the skein to sink into the water pastits upper edge is measured with a stopwatch (complete immersion time).The beginning and end of the measuring time are defined by the lowermostend of the skein and also its upper end passing the 1000 ml mark. Thisfirst measured value is called the C1 value (“value of the first wettingcycle”).

[0048] 3. Immediately after determination of the C1 value, the skein isremoved from the measuring cylinder, dabbed with cellulose and dried for1 hour at 40° C. in a recirculating air drying cabinet (Heraeus type UT5042 EK). Step 2 is then repeated. The resulting value in seconds of thecomplete immersion time is called the C2 value (“value of the secondwetting cycle”). Drying and determination of the complete immersion timeare then repeated again, the C3 value (“value of the third wettingcycle”) being obtained. If the complete immersion times (C1 to C3values) are above 180 seconds, the particular cycle is terminated.

[0049] Results

[0050] The individual wetting test is passed if the values for C1 to C3are under 5 seconds. The test results are set out in Table 1 for theadditives according to the invention and in Table II for knownadditives. The cold cloud points are set out in Table III. TABLE I Sinktest with PP skeins containing additives according to the inventionSkein Cu sink Sink Sink Sink weight weight Sink weight/ time time timeNo. Additive in g in g skein factor C1 in s C2 in s C3 in s 1 POE(10)propane-1,2- 1.5780 0.3263 0.2068 1.00 1.00 1.50 diol didodecanoate 2POE(12) propane-1,2- 1.3399 0.2768 0.2066 1.32 1.28 2.25 dioldidodecanoate 3 POE(10) propane-1,3- 1.5539 0.3209 0.2065 3.18 4.35 2.09diol didodecanoate 4 POE(7) propane-1,3- 1.2807 0.2632 0.2055 1.18 1.091.59 diol didecanoate

[0051] For comparison, the results of the skin test for known additivesaccording to DE 100 155 54 are set out in Table II. TABLE II Skein Cusink Sink Sink Sink Sink Sink weight weight Sink weight/ time time timetime time Additive in g in g skein factor 1 in s 2 in s 3 in s 4 in s 5in s 1.5% PEG- 1.7648 0.3630 0.2057 1.2 1.2 1.2 1.2 1.3 400-dilaurate1.5% PEG- 1.7758 0.3673 0.2068 1.2 1.2 1.2 1.2 1.3 400-dilaurate

[0052] TABLE III Cold cloud points of the additives according to theinvention Product Cold cloud point 1 2° C. 2 5° C. 3 3° C. 4 3° C. PEG400 dilaurate (comparison) Cloudy at 25° C.

[0053] A wicking test was also carried out and the water absorption ofadditive-containing nonwovens was measured to demonstrate theeffectiveness of the additives according to the invention. To this end,melt-blown nonwovens were produced from polypropylene (PP) fiberscontaining 2% by weight of internal hydrophilicizing additives.

[0054] Additive A is a diester based on PEG400 esterified with two mollauric acid in accordance with the teaching of Applicants' WO 01175199.

[0055] Additive B (invention) is a product started with diethyleneglycol, subsequently reacted with ethylene and propylene oxide and,finally, end-capped with lauric acid. In formula (I), this correspondsto the group CH₂CH₂—O—CH₂CH₂—O for C and to the EO and PO groups for B,the molecule containing a total of 7 mol EO and 2 mol PO per mol of theadditive. A is a lauric acid residue.

[0056] A nonwoven containing additive-free fibers was tested forcomparison.

[0057] A. Wicking Test

[0058] Preparation:

[0059] Cutting to Size of the Nonwoven Samples

[0060] Dimensions: 225×85 mm

[0061] Number: 4

[0062] Direction: lengthwise and across

[0063] Procedure:

[0064] 1. Place nonwoven sample in the frame

[0065] 2. Immerse nonwoven and frame in distilled water to a depth of 10mm

[0066] 3. Read off height of rise after 120 seconds

[0067] Results: Rise in mm Additive A 0 Additive B 30 No additive 0

[0068] The nonwovens containing the additive according to the inventionshow distinctly better hydrophilicization than the products containingthe known additive.

[0069] B. Water Absorption

[0070] The test used in a modified EDANA test (chapter 10.1-72):

[0071] Preparation:

[0072] Cutting of the Nonwoven Samples to Size:

[0073] Dimensions: 120 mm×120 mm

[0074] Number: 3

[0075] Weight: at least 1.0 g (several nonwovens)

[0076] Procedure:

[0077] 1. Weigh nonwoven samples

[0078] 2. Place in distilled water for 60 secs. (weight nonwovensamples)

[0079] 3. Hang vertically in machine direction and leave to drain for120 secs.

[0080] 4. Reweigh nonwoven samples

[0081] 5. Leave to dry for 24 hours

[0082] 6. Repeat steps 1 to 5 twice

[0083] Calculate absorption (water uptake capacity)/%:${X\quad \%} = {\frac{{{Wet}\quad {weight}} - {{dry}\quad {weight}}}{{Dry}\quad {weight}} \times 100}$

[0084] The water absorption results are set out in the following Table:Water absorption in % Additive A 1003 Additive B 935 No additive 129

[0085] Accordingly, the additives according to the invention showequally good water absorption to the known products and thus representan alternative to those products

1. An internal hydrophilicizing additive for syntheticpolyolefin-containing fibers which corresponds to general formula (I):A-B-C-B-A  (I) where a represents a group r-coo in which r is asaturated, branched or unbranched c₇₋₂₁ alkyl group, b represents agroup (C_(n)H_(2n)O)_(k) in which n is an integer of 2 to 4 and k has avalue of 1 to 15, and c is a linear or branched alkylene groupcontaining at least 2 and at most 6 carbon atoms which may also beinterrupted by one or more oxygen atoms.
 2. A hydrophilicizing additiveas claimed in claim 1, characterized in that, in formula (I), R is asaturated linear alkyl group containing 9 to 13 carbon atoms andpreferably 9 to 11 carbon atoms.
 3. A hydrophilicizing additive asclaimed in claims 1 and 2, characterized in that, in formula (I), k hasa value of 1 to 15, preferably 4 to 10 and more particularly
 5. 4. Ahydrophilicizing additive as claimed in claims 1 to 3, characterized inthat, in formula (I), C stands for CH₂—CH₂, CH₂—CH(CH₃), CH₂—CH₂—CH₂ or(CH₂)₄ groups.
 5. A hydrophilicizing additive as claimed in claims 1 to4, characterized in that, in formula (I), C stands for aCH₂—CH₂—O—CH₂—CH₂—O group.
 6. A hydrophilicizing additive as claimed inclaims 1 to 5, characterized in that, in formula (I), n has a value of2.
 7. A hydrophilicizing additive as claimed in claims 1 to 4,characterized in that, in formula (I), R is a linear alkyl groupcontaining 9 carbon atoms, k has a value of 5, n has a value of 2 and Cis a CH₂—CH₂(CH₃) group.
 8. A hydrophilicizing additive as claimed inclaims 1 to 4, characterized in that, in formula (I), R is a linearalkyl group containing 11 carbon atoms, k has a value of 5, n has avalue of 2 and C is a CH₂—CH₂(CH₃) group.
 9. A hydrophilicizing additiveas claimed in claims 1 to 4, characterized in that, in formula (I), A isa saturated, branched or unbranched alkyl group containing 7 to 21carbon atoms, B is a C₃H₆ group and C is a CH₂—CH₂—O—CH₂—CH₂—O group.10. A hydrophilicizing additive as claimed in claims 1 to 9,characterized in that the compounds of formula (I) have a cold cloudpoint below 12° C., preferably below 10° C. and more particularly below6° C.
 11. A hydrophilicizing additive as claimed in claims 1 to 10,characterized in that the compounds of formula (I) has a cold cloudpoint below 5° C. and preferably below 3° C.
 12. A hydrophilicizingadditive as claimed in claims 1 to 11, characterized in that, in formula(I), B stands for a mixture of ethylene oxide and propylene oxidegroups.
 13. A hydrophilicizing additive as claimed in claims 1 to 11,characterized in that. in formula (I), B stands for propylene oxidegroups.
 14. A process for the production of hydrophilicizing additivescorresponding to formula (I) in claim 1 for syntheticpolyolefin-containing fibers, characterized in that a diol selected fromthe group consisting of ethane-1,2-diol, propane-1,2-diol,propane-1,3-diol and butane-1,4-diol or diethylene glycol or dipropyleneglycol is reacted with alkoxides selected from the group consisting ofethylene oxide, propylene oxide and/or butylene oxide and the resultingreaction product is esterified with a saturated, linear or branchedfatty acid containing 8 to 22 carbon atoms.
 15. The use of compoundscorresponding to formula (I) in claim 1 for hydrophilicizing fibers orsheet-form materials completely or partly containing polyolefins.
 16. Aprocess for the production of articles completely or partly containingpolyolefins, characterized in that compounds corresponding to formula(I) are added to polymer granules completely or partly containingpolyolefins in quantities of 0.1 to 30% by weight, based on thegranules, followed by processing in known manner to fibers or films,preferably by extrusion.
 17. A process as claimed in claim 16,characterized in that the compounds of formula (I) are added to thepolymer granules in quantities of 1 to 15% by weight and moreparticularly in quantities of 1 to 2.5% by weight.
 18. A process asclaimed in claims 16 and 17, characterized in that the products obtainedby extrusion are contacted with water and subsequently dried.
 19. Aprocess as claimed in claim 18, characterized in that the productsobtained by extrusion are contacted with water at 80 to 90° C. or withsteam.